NASA to “slingshot’ around Earth in movie-like mission

A crack team of astronomers, researchers and amateur star gazers are preparing to track the historic flight of a NASA spacecraft as it skims over Australia later this month.

The OSIRIS-REx spacecraft is en route to the carbonaceous asteroid Bennu and the plan is to use Earth’s gravity to get it there. The spacecraft will come within 10,500 miles of Earth as it uses the planet’s gravity to slingshot itself toward its destination.

The maneuver is known as an Earth Gravity Assist and will allow the spacecraft “to match the speed of the Bennu asteroid,” says Professor Phil Bland from Curtain University in Western Australia, who will be watching the event unfold.

“It turns out with a slight modification to our cameras, and the help of some amateur astronomers in Australia, we should be able to see it, and track it as it flies over,” he told News.com.au.

Bland is a member of the OSIRIS-REx science team and also leads an Australian group called the Desert Fireball Network, which, as he puts it, “tracks fireballs coming through the atmosphere.”

Aside from sounding really cool, the project helps answer some fundamental questions about the origin of celestial materials that land on Earth.

“We don’t know where meteorites come from,” Bland said. Basically, we’ve got all these samples that land on Earth but we don’t know the journey they took to get here.

“So what we try to do with the fireball network, we track everything that comes through the atmosphere over a large fraction of Australia,” he said.

Automated observatories dotted across the country monitor anything that blazes through the sky, which gives astronomers a good idea of where meteorites will land and roughly where they came from in the solar system.

“It’s kind of like giving us a geological map of the solar system,” Bland said.

But on September 23, all telescopes and cameras will be firmly fixed on NASA’s OSIRIS-REx spacecraft as it gets flung overhead.

The rare encounter offers an opportunity to highlight the capabilities of the Desert Fireball Network and planetary science research in Australia, Bland said. And he hopes more members of the public will get involved in observing the flyover.

“It helps the NASA folks to get as many observations as they can as it comes overhead so they can test the trajectory,” he said. “So they can check the real observations match what they’re getting from the probe.”

And you won’t necessarily need a sophisticated telescope to join in on the fun either.

“It’s not going to be visible to the naked eye, but really any amateur astronomer with a half decent telescope should be able to do it,” the professor said. “Or a big lens on a regular camera like a telephonic lens, they should be able to pick it up and see it themselves.”

The OSIRIS-REx spacecraft was launched on September 8, 2016, and will take about another year to reach the asteroid Bennu. Once there it will spend about 12 months on the surface of the space rock, mapping and analyzing the asteroid before embarking on its return journey.

If all goes according to plan, it will return to Earth in 2023 carrying a sample from Bennu which could help us record the early history of the solar system and better understand the molecular precursors to the origin of life.

“One of the reasons we want to go to the asteroid is that these materials haven’t really been altered that much since the solar system formed so they can tell us a lot about how planets came together,” Bland said. “There’s a lot of really big questions we don’t have the answer to for that.”

And NASA says the fly-by will also give researchers a unique opportunity to observe our home planet.

“The team is eager and ready to execute the Earth Gravity Assist,” said Rich Burns, who is the OSIRIS-REx project manager at NASA’s Goddard Space Flight Center in Maryland.

“Not only will it be a significant change in trajectory putting OSIRIS-REx on track for rendezvous with Bennu, it also represents a unique opportunity for the OSIRIS-REx instruments to observe our home planet,” he said.

“It is fantastic that ground based observers are also taking the opportunity to image OSIRIS-REx.”

There are over 500,000 known asteroids in the solar system, so why did NASA choose Bennu?

At the time of the mission’s asteroid selection in 2008, there were over 7,000 known so-called near Earth objects (NEOs), but only 192 had orbits that meant they would be close enough to make them accessible.

The most primitive asteroids are carbon-rich and have not significantly changed since they formed nearly 4 billion years ago and Bennu happens to be one of the few known asteroids on the list which had the right carbon composition.

It also has a diameter of about 1,600 feet making it stable enough to host the spacecraft because asteroids with smaller diameters rotate more rapidly causing problems for a mission like this. For instance, with a diameter of less than 650 feet, an asteroid spins so rapidly that the loose material on its surface can be ejected from it.

While Bennu happens to be the Goldilocks candidate for this particular mission, even when it’s over, it probably won’t be the last we see of the asteroid.

“Bennu is also one of the most potentially hazardous asteroids,” NASA says. “As it has a relatively high probability of impacting the Earth late in the 22nd century.”

That might be a long way off, but in the meantime we’re set to get an early introduction.